Fluorometer with multiple detection channels

ABSTRACT

An optical sensor may have multiple detection channels to detect different characteristics of a fluid. For example, an optical sensor used in industrial cleaning and sanitizing applications may have multiple detection channels to detect when a system is both clean and properly sanitized. In one example, an optical sensor includes an optical emitter that directs light into a fluid, a first optical detector that detects light transmitted through the fluid, a second optical detector that detects light scattered by the fluid, and a third optical detector that detects fluorescent emissions emitted by the fluid. The optical emitter and optical detectors can be positioned around an optical analysis area. Depending on the application, the optical emitter may be positioned to direct light adjacent a wall of the optical analysis area rather than at a center of the optical analysis area, which may increase the strength of signal on the detection channels.

TECHNICAL FIELD

This disclosure relates to optical measuring devices and, moreparticularly, to fluorometers for monitoring the concentration of one ormore substances in a sample.

BACKGROUND

In cleaning and antimicrobial operations, commercial users (e.g.,restaurants, hotels, food and beverage plants, grocery stores, etc.)rely upon the concentration of a cleaning or antimicrobial product tomake the product work effectively. Failure of a cleaning orantimicrobial product to work effectively (for example due toconcentration issues) can cause a commercial user to perceive theproduct as lower quality. End consumers may also perceive the commercialprovider of such products as providing inferior services. In addition,commercial users may be investigated and/or sanctioned by governmentregulatory and health agencies. Accordingly, there is a need for asystem that can monitor the characteristics of fluid solutions, e.g., todetermine if the concentration of a product is within a specifiedconcentration range. The same may be true for other applications, suchas water care, pest control, beverage and bottling operations, oil andgas refining and processing operations, and the like.

One method of monitoring the concentration of a product relies onmonitoring the fluorescence of the product that occurs when the sample(and the product within the sample) is exposed to a predeterminedwavelength of light. For example, compounds within the product or afluorescent tracer added to the product may fluoresce when exposed tocertain wavelengths of light. The concentration of the product can thenbe determined using a fluorometer that measures the fluorescence of thecompounds and calculates the concentration of the chemical based on themeasured fluorescence.

Fluorometric spectroscopy concerns the detection of fluorescent lightemitted by a sample of interest. It involves using a beam of light,usually ultraviolet (UV) light, that excites the electrons in moleculesof certain compounds in the sample and causes them to emit light (i.e.,to “fluoresce”). There are several types of fluorometers for measuringemitted fluorescence. Fluorometers generally have of a source ofexcitation radiant energy and a detector with a signal processor and areadout device.

SUMMARY

In general, this disclosure is directed to fluorometric devices,systems, and techniques for monitoring fluid samples. A fluorometeraccording to the disclosure may include an optical emitter and multipleoptical detectors to monitor different characteristics of the fluidsample. For example, the fluorometer may include an optical emitter thatdetects light passing from the optical emitter and through the fluidsample to determine the concentration of a non-fluorescing species inthe fluid. The fluorometer may further include another optical detectorthat detects fluorescent emissions from the fluid sample to determinethe concentration of a fluorescing species in the fluid. By configuringthe fluorometer with multiple optical detectors, the fluorometer maymonitor different characteristics of a fluid under analysis. Forexample, when used to monitor water samples from an industrial cleaningand sanitizing operation, the fluorometer may determine if the flushingwater is both clean (e.g., sufficiently devoid of a product beingflushed) and contains a sufficient amount of sanitizer.

Although the design of the fluorometer can vary, in some applications,the fluorometer includes an optical emitter that is offset relative toan optical analysis area through which fluid flows. The optical emittermay be offset so that light emitted from the optical emitter is directedadjacent a wall of the optical analysis area rather than at a center ofthe optical analysis area. Such an arrangement may help minimize theamount of light emitted by the optical emitter that is reflected, forexample, due to fluid turbidity or wall surfaces in the optical analysisarea. In turn, this configuration may increase the strength of signalprovided by an optical detector detecting light from the opticalanalysis area.

In one example, an optical sensor is described that includes an opticalemitter, a first optical detector, a second optical detector, and athird optical detector. The optical emitter is configured to directlight into a fluid sample. The first optical detector is configured todetect light emitted by the optical emitter and transmitted through thefluid sample. The second optical detector is configured to detect lightemitted by the optical emitter and scattered by the fluid sample. Thethird optical detector is configured to detect fluorescent emissionsemitted by the fluid sample in response to the light emitted by theoptical emitter. According to the example, the optical sensor alsoincludes an optical emission filter positioned between the opticalemitter and the fluid sample, a first optical detection filterpositioned between the first optical detector and the fluid sample, asecond optical detection filter positioned between the second opticaldetector and the fluid sample, and a third optical detection filterpositioned between the third optical detector and the fluid sample. Theexample further specifies that the optical emission filter, the firstoptical detection filter, and the second optical detection filter areeach configured to filter out the same wavelengths of light so thatsubstantially any light detected by the first optical detector and thesecond optical detector is light emitted from the optical emitter andpassing through the fluid sample.

In another example, a method is described that includes emitting lightinto a fluid sample via an optical emitter. The example method alsoincludes detecting light emitted from the optical emitter andtransmitted through the fluid sample via a first optical detector,detecting light emitted from the optical emitter and scattered by thefluid sample via a second optical detector, and detecting fluorescentemissions emitted by the fluid sample in response to light emitted bythe optical emitter via a third optical detector. The example methodspecifies that detecting light via the first optical detector anddetecting light via the second optical detector further includesfiltering the light so that substantially any light detected by thefirst optical detector and the second optical detector is light emittedfrom the optical emitter and passing into the fluid sample.

In another example, an optical sensor system is described that includesa housing that defines an optical analysis area through which a fluidsample travels for optical analysis. The housing includes an opticalemitter assembly that carries an optical emitter configured to directlight into the fluid sample, a first optical emitter assembly thatcarries a first optical detector configured to detect light emitted bythe optical emitter and transmitted through the fluid sample, a secondoptical emitter assembly that carries a second optical detectorconfigured to detect light emitted by the optical emitter and scatteredby the fluid sample, and a third optical emitter assembly that carries athird optical detector configured to detect fluorescent emissionsemitted by the fluid sample in response to the light emitted by theoptical emitter. The housing also includes an optical emitter windowpositioned between the optical emitter and the optical analysis area, afirst optical detector window positioned between the first opticaldetector and the optical analysis area, a second optical detector windowpositioned between the second optical detector and the optical analysisarea, and a third optical detector window positioned between the thirdoptical detector and the optical analysis area. According to theexample, the first optical detector window is positioned on an oppositeside of the optical analysis area from the optical emitter window, thesecond optical detector window is positioned at an approximately 90degree angle relative to the optical emitter window, and the thirdoptical detector window is positioned on an opposite side of the opticalanalysis area from the second detector window.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating an example fluid system that includesan optical sensor according to examples of the disclosure.

FIG. 2 is a block diagram illustrating an example optical sensor thatmay be used in the example fluid system of FIG. 1.

FIG. 3 is a schematic drawing of an example physical configuration of anoptical sensor that may be used by the optical sensors in FIGS. 1 and 2.

FIGS. 4 and 5 are cross-sectional drawings of the optical sensor of FIG.3.

FIG. 6 is a cross-sectional drawing of an example alternativeconfiguration of the optical sensor of FIG. 3.

FIG. 7 is a cross-sectional drawing of an example alternativeconfiguration of the optical sensor of FIG. 6.

DETAILED DESCRIPTION

The following detailed description is exemplary in nature and is notintended to limit the scope, applicability, or configuration of theinvention in any way. Rather, the following description provides somepractical illustrations for implementing examples of the presentinvention. Examples of constructions, materials, dimensions, andmanufacturing processes are provided for selected elements, and allother elements employ that which is known to those of ordinary skill inthe field of the invention. Those skilled in the art will recognize thatmany of the noted examples have a variety of suitable alternatives.

Optical sensors are used in a variety of applications, includingmonitoring industrial processes. An optical sensor can be implemented asa portable, hand-held device that is used to periodically analyze theoptical characteristics of a fluid in an industrial process.Alternatively, an optical sensor can be installed online to continuouslyanalyze the optical characteristics of a fluid in an industrial process.In either case, the optical sensor may optically analyze the fluidsample and determine different characteristics of the fluid, such as theconcentration of one or more chemical species in the fluid.

As one example, optical sensors are often used in industrial cleaningand sanitizing applications. During an industrial cleaning andsanitizing process, water is typically pumped through an industrialpiping system to flush the piping system of product residing in pipesand any contamination build-up inside the pipes. The water may alsocontain a sanitizing agent that functions to sanitize and disinfect thepiping system. The cleaning and sanitizing process can prepare thepiping system to receive new product and/or a different product than waspreviously processed on the system.

An optical sensor can be used to monitor the characteristics of flushingand/or sanitizing water flowing through a piping system during anindustrial cleaning and sanitizing process. Either continuously or on anintermittent basis, samples of water are extracted from the pipingsystem and delivered to the optical sensor. Within the optical sensor,light is emitted into the water sample and used to evaluate thecharacteristics of the water sample. The optical sensor may determinewhether residual product in the piping system has been sufficientlyflushed out of the pipes, for example, by determining that there islittle or no residual product in the water sample. The optical sensormay also determine the concentration of sanitizer in the water sample,for example, by measuring a fluorescent signal emitted by the sanitizerin response to the light emitted into the water sample. If it isdetermined that there is an insufficient amount of sanitizer in thewater sample to properly sanitize the piping system, the amount ofsanitizer is increased to ensure proper sanitizing of the system.

This disclosure describes an optical sensor that, in some examples,includes multiple optical detectors providing multiple optical detectionchannels. Each optical detector is positioned at a different locationwithin the optical sensor relative to an optical emitter. For example,one optical detector may be positioned on an opposite side of a fluidchannel from the optical emitter to detect light emitted by the opticalemitter and transmitted through fluid within the fluid channel. Anotheroptical detector may be positioned at a 90 degree angle relative to theoptical emitter to detect light emitted by the optical emitter andscattered by fluid within the fluid channel. Yet another opticaldetector may be positioned at a different 90 degree angle relative tothe optical emitter to detect light fluorescent emissions emitted byfluid within the fluid channel in response to light from the opticalemitter.

By configuring the optical sensor with multiple optical detectionchannels, the optical sensor may comprehensively monitor fluid samplesfrom an industrial process. For instance, when implemented as part of anonline cleaning and sanitizing system, the optical sensor can receivefluid samples, such as samples of flushing water containing a sanitizingagent, and emit light into the fluid samples. The light detected by thedifferent optical detectors of the optical sensor in response to theemitted light may then vary depending on the characteristics of thefluid sample. For example, a fluid sample obtained at the start of thecleaning process may contain a significant amount of optically opaquematerial (e.g., residual product in a piping system) so that neither thetransmission detector nor the scattering detector receives any light. Asfluid samples extracted from the system become progressively cleaner,the transmission detector may detect increasing amounts of light passingthrough the fluid sample until the transmission detector becomessaturated with light. Around this point in the cleaning process,however, the scattering detector may begin detecting light scatteringwithin the fluid sample to allow continued monitoring of the fluidsample through the cleaning process. When the optical sensor furtherincludes a detector that detects fluorescent emissions, the opticalsensor can monitor the concentration of sanitization agent in the watersamples. In this manner, the optical sensor can use the differentoptical detectors to monitor progress of a cleaning and sanitizingoperation and the concentration of a sanitizing agent used in thecleaning and sanitizing operation. Of course, this is merely one exampleimplementation of the optical sensor, and other implementations are bothpossible and contemplated.

While the optical sensor can have a variety of different configurations,in some examples, the optical sensor is designed to have an opticalemitter that is offset from a center of a flow channel through which afluid sample travels. For example, the optical emitter may be arrangedto direct light adjacent to a wall of the flow channel rather than intoa center of the flow channel. When so configured, the light emitted intothe flow channel may be less likely to reflect off internal surfaces ofthe flow channel than when the light is directed into a center of theflow channel. In turn, this may increase the strength of the signaldetected by the optical detectors, providing stronger signals formonitoring the characteristics of the fluid under analysis. Inapplications where fouling builds up on an optical detector duringservice, the ability to generate stronger signals can extend the lengthof time the optical sensor can remain in service between cleaning andmaintenance.

Example optical sensor configurations will be described in greaterdetail below with respect to FIGS. 2-6. However, an example fluid systemincluding an example optical sensor system will first be described withrespect to FIG. 1.

FIG. 1 is a conceptual diagram illustrating an example fluid system 100,which may be used to produce a chemical solution having fluorescentproperties, such as a sanitizer solution exhibiting fluorescentproperties. Fluid system 100 includes optical sensor 102, a reservoir104, a controller 106, and a pump 108. Reservoir 104 may store aconcentrated chemical agent that can be blended with a diluent, such aswater, to generate the chemical solution. Optical sensor 102 isoptically connected to fluid pathway 110 and is configured to determineone or more characteristics of the solution traveling through the fluidpathway. In operation, optical sensor 102 can communicate withcontroller 106, and controller 106 can control fluid system 100 based onthe fluid characteristic information generated by the optical sensor.

Controller 106 is communicatively connected to optical sensor 102 andpump 108. Controller 106 includes processor 112 and memory 114.Controller 106 communicates with pump 108 via a connection 116. Signalsgenerated by optical sensor 102 are communicated to controller 106 via awired or wireless connection, which in the example of FIG. 1 isillustrated as wired connection 118. Memory 109 stores software forrunning controller 106 and may also store data generated or received byprocessor 112, e.g., from optical sensor 102. Processor 112 runssoftware stored in memory 114 to manage the operation of fluid system100.

As described in greater detail below, optical sensor 102 is configuredto optically analyze a sample of fluid flowing through fluid pathway110. In one example, optical sensor 102 includes an optical emitter thatemits light into the fluid sample and multiple optical detectors (e.g.,two, three, or more optical detectors) that measure light from the fluidsample. For example, optical sensor 102 may include an optical detectorthat is positioned to measure light emitted by the optical emitter andtransmitted through the fluid sample. Optical sensor 102 may furtherinclude an optical detector that is positioned to measure light emittedby the optical emitter and scattered in a direction substantiallyorthogonal to the direction of emission. Optical sensor 102 may stillfurther include an optical detector that is positioned and configured tomeasure fluorescent emissions emitted by the fluid sample. In operation,the optical detectors measuring light transmittance and scattering maybe used to measure the optical transparency of the fluid sample, whichmay indicate the cleanliness of the system from which the fluid samplewas extracted. The optical detector measuring fluorescence may be usedto measure the concentration of a chemical species (e.g., sanitizer,corrosion control agent) in the fluid sample. By providing multipleoptical detectors, optical sensor 102 may measure different opticalcharacteristics of the fluid sample, such as the amount of opticallyopaque material in the fluid sample (for example, contamination beingcleaned from a system) and a concentration of a chemical species in thefluid sample. In addition, the optical sensor 102 may measure theoptical transparency of the fluid sample across a wide range ofconcentrations of the optically opaque material.

Independent of the number of optical detectors in optical sensor 102, insome additional examples described in greater detail below, that opticalsensor has an optical emitter that is positioned to direct lightadjacent to a wall of an optical analysis area rather than in a centerof the optical analysis area. By moving the optical emitter so it isoffset from a center of the optical analysis area, light emitted by theoptical emitter may be less likely to reflect off internal surfaces inthe optical analysis area. In turn, this may increase the amount oflight received by an optical detector in optical sensor 102, increasingthe strength of the signal produced by the optical detector.

In the example of FIG. 1, fluid system 100 is configured to generate achemical solution having fluorescent properties. Fluid system 100 cancombine one or more concentrated chemical agents stored within reservoir104 with water or another diluting fluid to produce the chemicalsolutions. Example chemical solutions that may be produced by fluidsystem 100 include, but are not limited to, cleaning agents, sanitizingagents, cooling water for industrial cooling towers, biocides such aspesticides, anti-corrosion agents, anti-scaling agents, anti-foulingagents, laundry detergents, clean-in-place cleaners, floor coatings,vehicle care compositions, water care compositions, bottle washingcompositions, and the like.

The chemical solutions generated by fluid system 100 may emitfluorescent radiation in response to optical energy directed into thesolutions by optical sensor 102. Optical sensor 102 can then detect theemitted fluorescent radiation and determine various characteristics ofthe solution, such as a concentration of one or more chemical compoundsin the solution, based on the magnitude of the emitted fluorescentradiation. In order to enable optical sensor 102 to detect fluorescentemissions, the fluid generated by fluid system 100 and received byoptical sensor 102 may include a molecule that exhibits fluorescentcharacteristics. In some examples, the fluid includes a polycycliccompound and/or a benzene molecule that has one or more substituentelectron donating groups such as, e.g., —OH, —NH₂, and —OCH₃, which mayexhibit fluorescent characteristics. Depending on the application, thesecompounds may be naturally present in the chemical solutions generatedby fluid system 100 because of the functional properties (e.g., cleaningand sanitizing properties) imparted to the solutions by the compounds.

In addition to or in lieu of a naturally fluorescing compound, the fluidgenerated by fluid system 100 and received by optical sensor 102 mayinclude a fluorescent tracer (which may also be referred to as afluorescent marker). The fluorescent tracer can be incorporated into thefluid specifically to impart fluorescing properties to the fluid.Example fluorescent tracer compounds include, but are not limited to,naphthalene disulfonate (NDSA), 2-naphthalenesulfonic acid, Acid Yellow7,1,3,6,8-pyrenetetrasulfonic acid sodium salt, and fluorescein.

Independent of the specific composition of the fluid generated by fluidsystem 100, the system can generate fluid in any suitable fashion. Underthe control of controller 106, pump 108 can mechanically pump a definedquantity of concentrated chemical agent out of reservoir 104 and combinethe chemical agent with water to generate a liquid solution suitable forthe intended application. Fluid pathway 110 can then convey the liquidsolution to an intended discharge location. In some examples, fluidsystem 100 may generate a flow of liquid solution continuously for aperiod of time such as, e.g., a period of greater than 5 minutes, aperiod of greater than 30 minutes, or even a period of greater than 24hours. Fluid system 100 may generate solution continuously in that theflow of solution passing through fluid pathway 110 may be substantiallyor entirely uninterrupted over the period of time.

In some examples, monitoring the characteristics of the fluid flowingthrough fluid pathway 110 can help ensure that the fluid isappropriately formulated for an intended downstream application.Monitoring the characteristics of the fluid flowing through fluidpathway 110 can also provide feedback information, e.g., for adjustingparameters used to generate new fluid solution. For these and otherreasons, fluid system 100 can include a sensor to determine variouscharacteristics of the fluid generated by the system.

In the example of FIG. 1, fluid system 100 includes optical sensor 102.Optical sensor 102 is configured to determine one or morecharacteristics of the fluid flowing through fluid pathway 110. Examplecharacteristics include, but are not limited to, the concentration ofone or more chemical compounds within the fluid (e.g., the concentrationof one or more active agents added from reservoir 104 and/or theconcentration of one or more materials being flushed from piping influid system 100), the temperature of the fluid, the conductivity of thefluid, the pH of the fluid, the flow rate at which the fluid movesthrough the optical sensor, and/or other characteristics of the fluidthat may help ensure the system from which the fluid sample beinganalyzed is operating properly. Optical sensor 102 communicates detectedcharacteristic information to controller 106 via connection 118.

In response to receiving the detected characteristic, processor 112 ofcontroller 106 may compare the determined characteristic information toone or more thresholds stored in memory 114 such as one or moreconcentration thresholds. Based on the comparison, controller 106 mayadjust fluid system 100, e.g., so that the detected characteristicmatches a target value for the characteristic. In some examples,controller 106 starts and/or stops pump 108 or increases and/ordecreases the rate of pump 108 to adjust the concentration of a chemicalcompound flowing through fluid pathway 110. Starting pump 108 orincreasing the operating rate of pump 108 can increase the concentrationof the chemical compound in the fluid. Stopping pump 108 or decreasingthe operating rate of pump 108 can decrease the concentration ofchemical compound in the fluid. In some additional examples, controller106 may control the flow of water that mixes with a chemical compound inreservoir 104 based on determined characteristic information, forexample, by starting or stopping a pump that controls the flow of wateror by increasing or decreasing the rate at which the pump operates.Although not illustrated in the example fluid system 100 of FIG. 1,controller 106 may also be communicatively coupled to a heat exchanger,heater, and/or cooler to adjust the temperature of fluid flowing throughfluid pathway 110 based on characteristic information received fromoptical sensor 102.

Optical sensor 102 may be implemented in a number of different ways influid system 100. In the example shown in FIG. 1, optical sensor 102 ispositioned in-line with fluid pathway 110 to determine a characteristicof the fluid flowing through the fluid pathway. In other examples, apipe, tube, or other conduit may be connected between fluid pathway 110and a flow chamber of optical sensor 102. In such examples, the conduitcan fluidly connect the flow chamber (e.g., an inlet of the flowchamber) of optical sensor 102 to fluid pathway 110. As fluid movesthrough fluid pathway 110, a portion of the fluid may enter the conduitand pass adjacent a sensor head positioned within a fluid chamber,thereby allowing optical sensor 102 to determine one or morecharacteristics of fluid flowing through the fluid pathway. Whenimplemented to receive fluid directly from fluid pathway 110, opticalsensor 102 may be characterized as an online optical sensor. Afterpassing through the flow chamber, analyzed fluid may or may not bereturned to fluid pathway 110, e.g., via another conduit connecting anoutlet of the flow chamber to the fluid pathway.

In yet other examples, optical sensor 102 may be used to determine oneor more characteristics of a stationary volume of fluid that does notflow through a flow chamber of the optical sensor. For example, opticalsensor 102 may be implemented as an offline monitoring tool (e.g., as ahandheld sensor), that requires filling the optical sensor with a fluidsample manually extracted from fluid system 100.

Fluid system 100 in the example of FIG. 1 also includes reservoir 104,pump 108, and fluid pathway 110. Reservoir 104 may be any type ofcontainer that stores a chemical agent for subsequent deliveryincluding, e.g., a tank, a tote, a bottle, and a box. Reservoir 104 maystore a liquid, a solid (e.g., powder), and/or a gas. Pump 108 may beany form of pumping mechanism that supplies fluid from reservoir 104.For example, pump 108 may comprise a peristaltic pump or other form ofcontinuous pump, a positive-displacement pump, or any other type of pumpappropriate for the particular application. In examples in whichreservoir 104 stores a solid and/or a gas, pump 108 may be replaced witha different type of metering device configured to deliver the gas and/orsolid chemical agent to an intended discharge location. Fluid pathway110 in fluid system 100 may be any type of flexible or inflexibletubing, piping, or conduit.

In the example of FIG. 1, optical sensor 102 determines a characteristicof the fluid flowing through fluid pathway 110 (e.g., concentration of achemical compound, temperature or the like) and controller 106 controlsfluid system 100 based on the determined characteristic and, e.g., atarget characteristic stored in memory 114. FIG. 2 is block diagramillustrating an example of an optical sensor 200 that determines acharacteristic of a fluid medium. Sensor 200 may be used as opticalsensor 102 in fluid system 100, or sensor 200 may be used in otherapplications beyond fluid system 100.

With reference to FIG. 2, sensor 200 includes a controller 220, one ormore optical emitters 222 (referred to herein as “optical emitter 222”),and one or more optical detectors which, in the illustrated example, isshown as including three optical detectors: first optical detector 224A,second optical detector 224B, and third optical detector 224C(collectively referred to therein as “optical detectors 224”). Sensor200 also includes optical filters 225A-225D (collectively “opticalfilters 225”) positioned between optical emitter 222/optical detectors224 and optical analysis area 230. Controller 220 includes a processor226 and a memory 228. In operation, optical emitter 222 directs lightinto a fluid sample filling optical analysis area 230. The fluid samplemay be stationary within optical analysis area 230. Alternatively, thefluid sample may be flowing through optical analysis area 230.Regardless, in response to the light emitted by optical emitter 222, oneor more of the optical detectors 224 may detect light emanating from orpassing through the fluid. The characteristics of the fluid in opticalanalysis area 230 (e.g., the concentration of different chemical speciesin the fluid) may dictate whether light emitted by optical emitter 222reaches any or all of optical detectors 224. Further, the position andconfiguration of each of optical detectors 224 relative to opticalemitter 222 may influence whether the optical detectors detect lightemitted by optical emitter 222 during operation.

In some examples, optical sensor 200 includes additional emitters and/ordetectors. For example, optical sensor 200 may include a fourth detector224D that functions as a reference detector. In operation, fourthdetector 224D may receive unfiltered light from optical emitter 222 tomonitor the output intensity of the optical emitter. Controller 220 mayadjust measurements made by optical detectors 224A-224C to compensatefor changes in the output of optical emitter 222, as determined based ondata from fourth optical detector 224D.

Although sensor 200 is generally described as being an optical sensor,the sensor may include one or more non-optical sensor components formeasuring additional properties of a fluid flowing through the sensor.In the example of FIG. 2, sensor 200 includes a temperature sensor 221,a pH sensor 229, a conductivity sensor 231, and a flow sensor 232.Temperature sensor 221 may sense a temperature of the fluid flowingthrough the sensor; pH sensor 229 may determine a pH of the fluidflowing through the sensor; and conductivity sensor 231 may determine anelectrical conductivity of the fluid flowing through the sensor. Flowsensor 232 may monitor the flow rate at which fluid is flowing throughthe sensor.

In the configuration of sensor 200, first optical detector 224A, secondoptical detector 224B, and third optical detector 224C are eachpositioned on a different side of optical analysis area 230 than opticalemitter 222. In particular, first optical detector 224A is positioned onan opposite side of optical analysis area 230 than optical emitter 222(e.g., directly across the optical analysis area from the opticalemitter). Second optical detector 224B is positioned at an approximately90 degree angle relative to optical emitter 222. Further, third opticaldetector 224C is positioned on an opposite side of optical analysis area230 from second optical detector 224B and also at an approximately 90degree angle relative to optical emitter 222.

First optical detector 224A and second optical detector 224B in theexample of FIG. 2 are configured to detect light directed by opticalemitter 222 into fluid in optical analysis area 230 and passing throughthe fluid (e.g., either by direct transmission or byscattering/reflection). First optical detector 224A can detect lighttransmitted from optical emitter 222 across optical analysis area 230,such as light transmitted directly across the optical analysis area in asubstantially linear transmission path. Second optical detector 224B candetect light transmitted from optical emitter 222 andscattered/reflected by fluid within optical analysis area 230. Forexample, second optical detector 224B can detect light transmitted fromoptical emitter 222 and scattered in an orthogonal (e.g., approximately90 degree angle) relative to the direction of light emission. Thirdoptical detector 224C in the example of FIG. 2 is configured to detectfluorescent emissions generated by the fluid in optical analysis area230 in response to light from optical emitter 222.

In operation, first optical detector 224A and/or second optical detector224B may be used to determine a concentration of a non-fluorescingspecies in the fluid sample under analysis whereas third opticaldetector 224C may be used to determine a concentration of a fluorescingspecies in the fluid sample under analysis. The amount of light detectedby each of optical detectors 224 can be associated with differentchemical concentration levels stored in memory 228. Accordingly, duringuse, processor 226 can receive signals from each of optical detectors224 representative of the amount of light detected by each opticaldetector, compare and/or process the signals based on calibrationinformation stored in memory 228, and determine the concentration of oneor more chemical species in the fluid sample under analysis. Byproviding a first optical detector 224A and second optical detector 224Bon different sides of optical analysis area 230, sensor 200 maydetermine a concentration for a non-fluorescing species over a widerrange of concentrations than if the sensor includes only one of firstoptical detector 224A and second optical detector 224B.

As one example, sensor 200 may be used to monitor flushing water that isused to flush a piping system containing an optically opaque materialsuch as milk. Sensor 200 may receive and evaluate samples of theflushing water throughout the flushing process. At the beginning of theflushing process, sensor 200 may receive a fluid sample that contains ahigh concentration of the optically opaque material. When opticalemitter 222 directs light into this fluid sample, neither first opticaldetector 224A nor second optical detector 224B may detect any light,indicating that there is a high concentration of the optically opaquematerial in the sample. As the optically opaque material begins to clearfrom the piping system, sensor 200 may receive a fluid sample thatcontains a reduced amount of optically opaque material. When opticalemitter 222 directs light into this fluid sample, first optical detector224A may detect some light transmitting through the fluid sample andsecond optical detector 224B may or may not detect light scatteringwithin the fluid sample. Sensor 200 can determine a concentration of theoptically opaque material, e.g., based on a magnitude of the signalreceived from first optical detector 224A and calibration data stored inmemory.

As the flushing process continues in this example, the optically opaquematerial may further clear from the piping system, e.g., until thepiping system is substantially or entirely clear of the optically opaquematerial. Accordingly, sensor 200 may receive an additional fluid samplethat contains a further reduced amount of optically opaque material.When optical emitter 222 directs light into this fluid sample, theamount of light passing through the fluid sample may saturate firstoptical detector 224A because the optical transparency of the fluidsample is so great. However, second optical detector 224B may detectlight scattering within the fluid sample. The amount of light scatteringmay be dependent, e.g., on the concentration of the optically opaquematerial in the fluid sample and/or the turbidity of the fluid sample.Sensor 200 can determine a concentration of the optically opaquematerial, e.g., based on a magnitude of the signal received from secondoptical detector 224B and calibration data stored in memory.

In instances in which the flushing liquid also includes a fluorescingmolecule, for example associated with a sanitizing agent, third opticaldetector 224C may detect fluorescent emissions emanating from the fluidsample in response to light emitted by optical emitter 222. Sensor 200may then determine a concentration of the fluorescing material, e.g.,based on a magnitude of the signal received from third optical detector224A and calibration data stored in memory. In this way, sensor 200 canprovide multiple detection channels associated with multiple opticaldetectors. The different optical detectors may be configured andarranged relative to optical emitter 222 to detect light traveling indifferent directions and/or different wavelengths of light. It should beappreciated that the foregoing discussion of a flushing process ismerely one example implementation of sensor 200, and the disclosure isnot limited in this respect.

To control the wavelengths of light emitted by optical emitter 222 anddetected by optical detectors 224, sensor 200 may include opticalfilters 225. Optical filters 225 can filter wavelengths of light emittedby optical emitter 222 and/or received by optical detectors 224, e.g.,so that only certain wavelengths of light are emitted into opticalanalysis area 230 and/or received from the optical analysis area. In theexample of FIG. 2, a first optical detection filter 225A is positionedbetween first optical detector 224A and optical analysis area 230; asecond optical detection filter 225B is positioned between secondoptical detector 224B and the optical analysis area; a third opticaldetection filter 225C is positioned between third optical detector 224Cand the optical analysis area; and an optical emission filter 225D ispositioned between optical emitter 222 and the optical analysis area. Inoperation, light emitted by optical emitter 222 passes through opticalemission filter 225D. Optical emission filter 225D can filter out orremove certain wavelengths of light emitted by the optical emitter sothat only select wavelengths of light pass through the filter. Likewise,optical detection filters 225A-225C can filter out or remove certainwavelengths of light so that only select wavelengths of light arereceived by optical detectors 224. When used, reference optical detector224D can be positioned in a variety of locations within sensor 200. Indifferent examples, reference optical detector 224D can be positioned toreceive a portion of the light emitted by optical emitter 222 but notfiltered, a portion of the light reflected by filter 225D, and/or aportion of the light transmitted through filter 225D from opticalemitter 222.

The wavelengths of light that optical filters 225 are designed to filterout may vary, e.g., depending on the expected chemical composition ofthe fluid in optical analysis area 230 and the design parameters ofoptical emitter 222 and optical detectors 224. In applications wherefirst optical detector 224A and second optical detector 224B areconfigured to detect light passing through a fluid sample, first opticaldetection filter 225A and second optical detection filter 225B may beconfigured to pass the same wavelengths of light passing through opticalemission filter 225D while rejecting all other wavelengths of light. Bycontrast, third optical detection filter 225C may be configured toreject (e.g., filter out) those wavelengths of light emitted by opticalemitter 222 and pass different wavelengths of light corresponding to theportion of the spectrum in which a fluorescing molecule in the fluidsample emits. Third optical detection filter 225C may filter outdifferent wavelengths of light than optical emission filter 225D becausewhen optical emitter 222 directs light at one frequency (e.g.,ultraviolet frequency) into fluid flowing through optical analysis area230, fluorescing molecules may emit light energy at a differentfrequency (e.g., visible light frequency, a different ultravioletfrequency).

In practice, first optical filter 225A, second optical filter 225B, andoptical emission filter 225D may each be the same type of filter thatfilters out the same wavelengths of light. By contrast, third opticalfilter 225C may be configured to reject (e.g., filter out) allwavelengths of light that can pass through first optical filter 225A,second optical filter 225B, and optical emission filter 225D and allowpassage of wavelengths of light in a portion of the spectrum afluorescing molecule in the fluid sample is expected to emit. Forexample, first optical filter 225A, second optical filter 225B, andoptical emission filter 225D may each be configured to filter outwavelengths of light greater than 300 nanometers so that onlywavelengths of light less than 300 nanometers can pass through thefilters. In accordance with this example, third optical detector filter225C may filter out wavelengths of light less than 300 nanometers sothat only wavelengths of light greater than 300 nanometers can passthrough the filter.

By configuring first optical filter 225A and second optical filter 225Bto be the same optical filter as optical emission filter 225D,substantially any light (e.g., all light) detected by first opticaldetector 224A and second optical detector 224B during operation will belight emitted by optical emitter 222 that passes through opticalemission filter 225D and the fluid sample. Further, by configuring thirdoptical filter 225C to reject wavelengths of light passing throughoptical emission filter 225D, substantially any light (e.g., all light)detected by third optical detector 224C will be light emitted byfluorescing molecules in the fluid sample. In contrast, if first opticalfilter 225A and second optical filter 225B were to pass differentwavelengths of light than optical emission filter 225D, first opticaldetector 224A and second optical detector 224B may detect light fromsources other than optical emitter 222, such as light emitted byfluorescing molecules. Likewise, if third optical filter 225C were topass wavelengths of light emitted by optical emitter 222, third opticaldetector 224C may detect light from sources other than fluorescingmolecules, such as light emitted by the optical emitter itself.

In some examples, all three filters 225A, 225B, 225C are configured toreject wavelengths of light passing through optical emission filter 225Dso that substantially any light (e.g., all light) detected by all threeoptical detectors 224A, 224B, 224C will be light emitted by fluorescingmolecules in the fluid sample. Such a configuration may be used todetect multiple (e.g., three) different spectral areas of fluorescenceto measure multiple spectral components simultaneously. For instance,signals from one or two detectors measuring different spectral areas maybe used to compensate for interference from compounds present in a fluidand producing fluorescence masking a desired signal from the thirddetector. As an example, fluorescence from natural substances such asmilk may be present in a fluid and can interfere with fluorescenceemitted from a chemical compound in the fluid (e.g., a cleaning agent,sanitizing agent, tracer) whose concentration is being measured bysensor 200. To help compensate for this fluorescence masking, differentspectral areas (e.g., different wavelengths) of the fluorescentemissions from the fluid can be detected and used to computationallycompensate for the interference.

While sensor 200 in the example of FIG. 2 includes optical filters 225,in other examples, sensor 200 may not include optical filters 225 or mayhave a different number or arrangement of optical filters. For example,the physical filter positioned between optical emitter 222 and opticalanalysis area 230 may not be needed if a laser light source is usedproviding a highly monochromatic excitation beam. Additionally, some orall of optical filters 225A-225C for the detectors may not be needed ifthe spectral sensitivity of the detector(s) provides adequate rejectionof excitation light and/or fluorescence light. As another example, ifsensor 200 is configured to measure time delayed fluorescence orscattering, time filtration can be used instead of physical spectralfiltration. In such cases, the optical filters 225 may be programsstored in memory 228 that are executed by processor 226 toelectronically filter data generated by sensor 200.

Sensor 200 in FIG. 2 includes optical emitter 222. Optical emitter 222can emit optical energy into a fluid present with optical analysis area230. In some examples, optical emitter 222 emits optical energy over arange of wavelengths. In other examples, optical emitter 222 emitsoptical energy at one or more discrete wavelengths. For example, opticalemitter 222 may emit at two, three, four or more discrete wavelengths.Further, although sensor 200 is only illustrated as having only a singleoptical emitter, in other applications, sensor 200 may have a plurality(e.g., two, three, four, or more) of optical emitters.

In one example, optical emitter 222 emits light within the ultraviolet(UV) spectrum and/or in the visible range of the spectrum. Light withinthe UV spectrum may include wavelengths in the range from approximately200 nm to approximately 400 nanometers. Light within the visiblespectrum may include wavelengths in the range from approximately 400 nmto approximately 700 nm. Light emitted by optical emitter 222 isdirected into fluid within optical analysis area 230. In response toreceiving the optical energy, fluorescing molecules within the fluid mayexcite, causing the molecules to produce fluorescent emissions. Forexample, the light directed into the fluid by optical emitter 222 maygenerate fluorescent emissions by exciting electrons of fluorescingmolecules within the fluid, causing the molecules to emit energy (i.e.,fluoresce). The fluorescent emissions, which may or may not be at adifferent frequency than the energy emitted by optical emitter 222, maybe generated as excited electrons within fluorescing molecules changeenergy states. The energy emitted by the fluorescing molecules may bedetected by third optical detector 224C.

Optical emitter 222 may be implemented in a variety of different wayswithin sensor 200. Optical emitter 222 may include one or more lightsources to excite molecules within the fluid. Example light sourcesinclude light emitting diodes (LEDS), lasers, and lamps. In someexamples, as discussed above, optical emitter 222 includes an opticalfilter to filter light emitted by the light source. The optical filtermay be positioned between the light source and the fluid and be selectedto pass light within a certain wavelength range. In some additionalexamples, the optical emitter includes a collimator, e.g., a collimatinglens, hood or reflector, positioned adjacent the light source tocollimate the light emitted from the light source. The collimator mayreduce the divergence of the light emitted from the light source,reducing optical noise.

Sensor 200 also includes optical detectors 224. Optical detectors 224may include at least one optical detector that detects fluorescentemissions emitted by excited molecules within optical analysis area 230(e.g., third optical detector 224C) and at least one optical detectorthat detects light emitted by optical emitter 222 and passing throughfluid in the optical analysis area (e.g., first optical detector 224Aand/or second optical detector 224B). In operation, the amount ofoptical energy detected by each optical detector of optical detectors224 may depend on the contents of the fluid within optical analysis area230. If the optical analysis area contains a fluid solution that hascertain properties (e.g., a certain chemical compound and/or a certainconcentration of a chemical species), each optical detector of opticaldetectors 224 may detect a certain level of fluorescent energy emittedby the fluid and/or transmitted through or scattered by the fluid.However, if the fluid solution has different properties (e.g., adifferent chemical compound and/or a different concentration of thechemical species), each optical detector of optical detectors 224 maydetect a different level of fluorescent energy emitted by the fluidand/or a different level of optical energy transmitted through orscattered by the fluid. For example, if a fluid within optical analysisarea 230 has a first concentration of a fluorescing chemicalcompound(s), third optical detector 224C may detect a first magnitude offluorescent emissions. However, if the fluid within optical analysisarea 230 has a second concentration of the fluorescing chemicalcompound(s) that is greater than the first concentration, third opticaldetector 224C may detect a second magnitude of fluorescent emissionsthat is greater than the first magnitude.

Each optical detector of optical detectors 224 may be implemented in avariety of different ways within sensor 200. Each optical detector ofoptical detectors 224 may include one or more photodetectors such as,e.g., photodiodes or photomultipliers, for converting optical signalsinto electrical signals. In some examples, each optical detector ofoptical detectors 224 includes a lens positioned between the fluid andthe photodetector for focusing and/or shaping optical energy receivedfrom the fluid. In addition, while sensor 200 in the example of FIG. 2includes three optical detectors 224A-224C, in other examples, sensor200 may include fewer optical detectors (e.g., a single optical detectorsuch as 224B or 224C) or more optical detectors (e.g., four, five, ormore). It should be appreciated that the disclosure is not limited to asensor having any specific number of optical detectors.

Sensor 200 in the example of FIG. 2 also includes temperature sensor221. Temperature sensor 221 is configured to sense a temperature of afluid passing through a flow chamber of the sensor. In various examples,temperature sensor 221 may be a bi-metal mechanical temperature sensor,an electrical resistance temperature sensor, an optical temperaturesensor, or any other suitable type of temperature sensor. Temperaturesensor 221 can generate a signal that is representative of the magnitudeof the sensed temperature.

Controller 220 controls the operation of optical emitter 222 andreceives signals concerning the amount of light detected by each opticaldetector of optical detectors 224. Controller 220 also received signalsfrom temperature sensor 221 concerning the temperature of the fluid incontact with the sensor, signals from pH sensor 229 concerning the pH ofthe fluid in contact with the sensor, signals from conductivity sensor231 concerning the conductivity of the fluid in contact with the sensor,and signals from flow sensor 232 concerning the rate at which liquid isfollowing through the sensor. In some examples, controller 220 furtherprocesses signals, e.g., to determine a concentration of more or morechemical species within the fluid passing through fluid channel 230.

In one example, controller 220 controls optical emitter 222 to directradiation into a fluid and further controls each optical detector ofoptical detectors 224 to detect fluorescent emissions emitted by thefluid and/or light transmitted through or scattered by the fluid.Controller 220 then processes the light detection information. Forexample, controller 220 can process the light detection informationreceived from third optical detector 224C to determine a concentrationof a chemical species in the fluid. In instances in which a fluidincludes a fluorescent tracer, a concentration of a chemical species ofinterest can be determined based on a determined concentration of thefluorescent tracer. Controller 220 can determine a concentration of thefluorescent tracer by comparing the magnitude of fluorescent emissionsdetected by third optical detector 224C from a fluid having an unknownconcentration of the tracer to the magnitude of the fluorescentemissions detected by third optical detector 224C from a fluid having aknown concentration of the tracer. Controller 220 can determine theconcentration of a chemical species of interest using Equations (1) and(2) below:

$\begin{matrix}{C_{c} = {C_{m} \times \frac{C_{o}}{C_{f}}}} & {{Equation}\mspace{14mu} 1} \\{C_{m} = {K_{m} \times \left( {S_{x} - Z_{o}} \right)}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

In Equations (1) and (2) above, C_(c) is a current concentration of thechemical species of interest, C_(m) is a current concentration of thefluorescent tracer, C_(o) is a nominal concentration of the chemicalspecies of interest, C_(f) is a nominal concentration of the fluorescenttracer, K_(m) is a slope correction coefficient, S_(x) is a currentfluorescent measurement signal, and Z_(o) is a zero shift. Controller220 may further adjust the determined concentration of the chemicalspecies of interest based on the temperature measured by temperaturesensor 221.

Controller 220 may also process light detection information receivedfrom first optical detector 224A and/or second optical detector 224B todetermine other aspects of the fluid under analysis, such as aconcentration of a non-fluorescing chemical species in the fluid.Controller 220 can determine a concentration of the non-fluorescingchemical species by comparing the magnitude of light detected by firstoptical detector 224A and/or second optical detector 224B from a fluidhaving an unknown concentration of the species to the magnitude of lightdetected by first optical detector 224A and/or second optical detector224B from a fluid having a known concentration of the species.Controller 220 may compare the determined concentration to one or morethresholds stored in memory 228. For example, when controller 220 isused to monitor flushing water, the controller may compare thedetermined concentration of the non-fluorescing species to one or morethresholds stored in memory. Controller 220 may further adjust theflushing process (e.g., to start, stop, or adjust flushing water rates)based on the comparison.

Optical analysis area 230 in sensor 200 may be a region of the sensorwhere fluid can reside and/or pass through for optical analysis. In oneexample, optical analysis area 230 comprises a tube of opticallytransparent material (e.g., glass, plastic, sapphire) through whichlight can be emitted and received. The tube may define an internaldiameter and an external diameter, where a wall thickness of the tubeseparates the internal diameter from the external diameter. In anotherexample, optical analysis area 230 is a region of a flow chamber housingthrough which liquid flows for optical analysis. Although opticalanalysis area 230 is conceptually illustrated as being square incross-sectional shape, the area can define any polygonal (e.g.,triangle, hexagon) or arcuate (e.g., circular, elliptical) shape or evencombinations of polygonal and arcuate shapes. In addition, while opticalanalysis area 230 can be of any size, in some applications, the opticalanalysis area is comparatively small to minimize the amount of fluidthat is needed to fill the optical analysis area. For example, opticalanalysis area 230 may define a major cross-sectional dimension (e.g.,diameter) less than 15 millimeters (mm), such as less than 10 mm, orless than 5 mm. In one example, optical analysis area 230 is a tubehaving an outer diameter ranging from approximately 10 mm toapproximately 4 mm, a wall thickness ranging from approximately 3 mm toapproximately 1 mm, and an internal diameter ranging from approximately9 mm to approximately 1 mm.

Memory 228 of sensor 200 stores software and data used or generated bycontroller 220. For example, memory 228 may store data used bycontroller 220 to determine a concentration of one or more chemicalcomponents within the fluid being monitored by sensor 200. In someexamples, memory 228 stores data in the form of an equation that relateslight detected by optical detectors 224 to a concentration of one ormore chemical components.

Processor 226 runs software stored in memory 228 to perform functionsattributed to sensor 200 and controller 220 in this disclosure.Components described as processors within controller 220, controller106, or any other device described in this disclosure may each includeone or more processors, such as one or more microprocessors, digitalsignal processors (DSPs), application specific integrated circuits(ASICs), field programmable gate arrays (FPGAs), programmable logiccircuitry, or the like, either alone or in any suitable combination.

Sensor 102 (FIG. 1) and sensor 200 (FIG. 2) can have a number ofdifferent physical configurations. FIG. 3 is a schematic drawing of oneexample configuration of a sensor 300, which can be used by sensor 102and sensor 200. Sensor 300 includes a flow chamber 302, a lightemission/detection assembly 304, a flow chamber top cover 306, and aflow chamber bottom cover 308. Flow chamber 302 has an inlet 310 thatreceives fluid (e.g., from fluid pathway 110 in FIG. 1), an outlet 312that discharges the fluid after optical analysis inside of the flowchamber, and an optical analysis area 314 between the inlet and outlet.

Light emission/detection assembly 304 is shown outside of and insertableinto flow chamber 302. Light emission/detection assembly 304 includes anoptical emitter assembly 316 that carries an optical emitter, a firstoptical detector assembly 318 that carries a first optical detector, asecond optical detector assembly 320 that carries a second opticaldetector, and a third optical detector assembly 322 that carries a thirdoptical detector. In operation, the optical emitter carried by opticalemitter assembly 316 can emit optical energy through a first opticalwindow 324 into optical analysis area 314. This first optical window 324may be referred to as an optical emitter window. The first opticaldetector carried by the first optical detector assembly 318 can detectlight emitted by the optical emitter and transmitted across opticalanalysis area 314 and received through a second optical window 326. Thissecond optical window 326 may be referred to as a first optical detectorwindow. The second optical detector carried by the second opticaldetector assembly 320 can detect light emitted by the optical emitterand scattered in a direction substantially orthogonal to the directionof emission through a third optical window 328. This third opticalwindow 328 may be referred to as a second optical detector window. Inaddition, the third optical detector carried by the third opticaldetector assembly 322 can detect fluorescent emissions from withinoptical analysis area 314 through a fourth optical window 330. Thisfourth optical window 330 may be referred to as a third optical detectorwindow.

Optical windows 324, 326, 328, and 330 are shown as being positionedoutside of flow chamber 302 and insertable into the flow chamber. Wheninserted into the flow chamber, the optical windows may define fluidtight, optically transparent regions through which light can be emittedinto optical analysis area 314 and detected from the optical analysisarea. Optical windows 324, 326, 328, and 330 may or may not include alens, prism, or other optical device that transmits and refracts light.In the illustrated example, optical windows 324, 326, 328, and 330 areformed by a ball lens positioned within an insertion channel extendingthrough flow chamber 302. The ball lenses can be fabricated from glass,sapphire, or other suitable optically transparent materials. Indifferent examples, optical windows 324, 326, 328, and 330 may not beremovable but may instead be permanently formed/mated with flow chamber302.

In addition to flow chamber 302 and light emission/detection assembly304, sensor 300 in the example of FIG. 3 also includes an electricalconnection board 332, an electrical cable 334, and a temperature sensor336. Electrical connection board 332 electrically couples opticalemitter assembly 316, first optical detector assembly 318, secondoptical detector assembly 320, and third optical detector assembly 322to electrical cable 334. Electrical cable 334 may convey electricalsignals transmitted to or generated by sensor 300. Electrical cable 334may or may not also convey power to sensor 300 to power the variouscomponents of the sensor. Temperature sensor 336 can sense a temperatureof the fluid entering optical analysis area and generate a signalcorresponding to the sensed temperature.

FIG. 4 is a cross-sectional illustration of sensor 300 taken in a Z-Yplane indicated on FIG. 3 that bisects third optical window 328 andfourth optical window 330. Like components of sensor 300 in FIGS. 3 and4 are identified by like reference numbers. As shown in FIG. 4, opticalwindows 324, 328, and 330 are each positioned within flow chamber 302 todirect light into or to receive light from optical analysis area 314.Optical analysis area 314 is a flow path defined in flow chamber 302through which fluid can travel past the optical windows of the sensorfor optical analysis. In the illustrated example, optical windows 324,328, and 330 are positioned at a co-planar location (i.e., co-planar inthe X-Y plane indicated on FIG. 4) along optical analysis area 314,e.g., so that a common plane extends through a geometric center ofoptical windows 324, 328, and 330. Second optical window 326 (notillustrated on FIG. 4) may be positioned in the same plane as opticalwindows 324, 328, and 330. Positioning optical windows 324, 326, 328,and 330 in a common plane may be useful so that the optical detectorspositioned behind optical windows 326, 328, and 330 receive light fromthe same plane in which the optical emitter positioned behind opticalwindow 324 emits into. If optical windows 326, 328, and 330 are offsetfrom the plane in which optical window 324 is positioned, the amount oflight detected by, and hence the strength of signal generated by, thedetectors positioned behind the windows may be reduced as compared to aco-planar location.

While optical sensor 300 is illustrated as only having a single row ofoptical windows 324, 326, 328, and 330 positioned in a common plane foroptical emitter 222 and optical detectors 224, in examples in which theoptical sensor has more optical emitters and/or detectors, the sensorcan have one or more additional rows of optical windows. For example,optical sensor 300 may include two, three, or more vertically stacked(i.e., in the Z-direction indicated on FIG. 4) rows of optical windows,where optical windows in each row are co-planar (i.e., co-planar in theX-Y plane indicated on FIG. 4). In one example, optical sensor 300includes three rows of optical windows, where each row includes oneoptical emitter and three optical detectors. As another example, opticalsensor 300 includes two rows of optical windows, where each row includestwo optical emitters and two optical detectors. Increasing the number ofoptical emitters and/or optical detectors in sensor 300 can increase thenumber of wavelengths of light emitted in and/or detected from fluidflowing through fluid pathway 314.

FIG. 4 also illustrates temperature sensor 336. Temperature sensor 336is positioned within a common well 335 of optical housing 302 thatcontains optical detector 358. Temperature sensor 336 extends through abottom of the well so that the sensor contacts fluid flowing through theoptical sensor to sense a temperature of the fluid. In the example, thetemperature sensor 336 is formed on a circuit board 339, which is thesame circuit board containing optical detector 358. That is, a singlecircuit board contains the same electronics for the temperature sensoras the optical detector. Such a configuration may be useful to make amore compact optical sensor.

In some examples, sensor 300 includes additional non-optical sensorcomponents, such as a pH sensor, a conductivity sensor, and a flowsensor. When used, each of the non-optical sensors may be formed on acommon circuit board with one of the optical emitters (e.g., theelectronics for one of the optical emitters) and/or optical detectors(e.g., electronics for the optical detectors) of the sensor positionedwithin a common well of the housing. For example, electronic componentsfor the pH sensor may be formed on the same circuit board as one opticaldetector, electronic components for the conductivity sensor may beformed on the same circuit board as a different optical detector, andelectronic components for temperature sensor 336 may be formed oncircuit board 339 of yet another optical detector. Each sensor mayextend through a bottom of a respective well of optical housing 102(e.g., as shown for temperature sensor 336 in FIG. 4) to contact fluidflowing through the sensor. When used, the flow sensor may also beformed on the same circuit board as one of the optical emitters/opticaldetectors. As an example, electronics for a differential pressure flowsensor may be formed on the same circuit board as one of the opticalemitters/optical detectors with the flow sensor positioned in region 337to measure flow adjacent outlet 312.

FIG. 5 is a cross-sectional illustration of sensor 300 taken along theA-A line indicated on FIG. 4. Again, like components of sensor 300 inFIGS. 3-5 are identified by like reference numbers. As shown in thisexample, an optical emitter 350 is positioned (e.g., centered) behindfirst optical window 324, and a first optical detector 352 is positioned(e.g., centered) behind second optical window 326. First opticaldetector 352 is positioned on an opposite side of optical analysis area314, e.g., so that light emitted from optical emitter 350 traveling in alinear or substantially linear direction and transmitted through fluidin the optical analysis area is received by the first optical detector.In some examples, first optical detector 352 is positioned on anopposite side of optical analysis area 314 so that an axis 380 locatedin a common plane of optical windows 324, 326, 328, 330 (e.g., a commonX-Y plane indicated on FIGS. 4 and 5) and extending through a geometriccenter of first optical window 324 intersects second optical window 326across optical analysis area 314. For example, axis 380 extendingthrough a geometric center of first optical window 324 may intersect anaxis 382 that is located in the common plane of optical windows 324,326, 328, 330 and that extends through a geometric center of secondoptical window 326. In such a configuration, second optical widow 326may be positioned directly across the optical analysis area 314 fromfirst optical window 324. In other examples, as described in greaterdetail below with respect to FIG. 6, second optical window 326 may bepositioned across optical analysis area 314 from first optical window324 but may be offset from the first optical window (e.g., in thepositive or negative Y-direction indicated on FIG. 5).

In the example of FIG. 5, sensor 300 also includes a second opticaldetector 356 positioned (e.g., centered) behind the third optical window328 and a third optical detector 358 positioned (e.g., centered) behindthe fourth optical window 330. Second optical detector 356 is positionedat an approximately 90 degree angle with respect to optical emitter 350,e.g., so that light emitted from optical emitter 350 traveling in alinear or substantially linear direction must scatter in a generallyorthogonal direction and be transmitted through fluid in the opticalanalysis area in order to be received by the second optical detector.Third optical detector 358 is positioned opposite second opticaldetector 356 across optical analysis area 314. Third optical detector358 is also positioned at an approximately 90 degree angle with respectto optical emitter 350, e.g., so that light emitted from optical emitter350 traveling in a linear or substantially linear direction must scatterin a generally orthogonal direction and be transmitted through fluid inthe optical analysis area in order to be received by the third opticaldetector.

In some examples, second optical detector 356 is positioned at anapproximately 90 degree angle with respect to optical emitter 350 sothat an axis 384 in a common plane of optical windows 324, 326, 328, 330(e.g., a common X-Y plane indicated on FIGS. 4 and 5) and extendingthrough a geometric center of third optical window 328 intersects axis380 at an approximately 90 degree angle (e.g., an angle ranging from 60degrees to 120 degrees). Third optical detector 358 may be positioned atan approximately 90 degree angle with respect to optical emitter 350 sothat an axis 386 in a common plane of optical windows 324, 326, 328, 330(e.g., a common X-Y plane indicated on FIGS. 4 and 5) and extendingthrough a geometric center of fourth optical window 330 intersects axis380 at an approximately 90 degree angle (e.g., an angle ranging from 60degrees to 120 degrees). In different examples, axis 384 and axis 386may intersect one another so that the third optical window is positioneddirectly across from the fourth optical window, or axis 384 and axis 386may be offset from one another (e.g., in the positive or negativeX-direction indicated on FIG. 5) so that third optical window is offsetfrom fourth optical window. Positioning third optical window 328 andfourth optical window 330 (and the corresponding detectors positionedbehind the optical windows) at an angle relative to first optical window324 (and the corresponding optical emitter positioned behind the window)may be useful to limit the amount of light received by the detectors. Ifthe detectors receive too much light, the detectors may become saturatedand cease providing useful analysis information.

When sensor 300 is arranged as illustrated in FIG. 5, optical emitter350 and optical detectors 352, 356, 358 may each be centered aboutoptical analysis area 314 so as to emit light towards and receive lightfrom a geometric center of the optical analysis area. Such aconfiguration may be useful for providing a central area of opticalinspection into which light is directed and received during operation ofsensor 300. In other examples, however, one or more of optical emitter350 and optical detectors 352, 356, 358 may be offset from opticalanalysis area 314 so that light is not emitted towards and/or receivedfrom a center of the optical analysis area but rather at an off-centerregion of the optical analysis area.

Applicant has found that, in some examples, moving an optical emitter sothat the emitter directs light adjacent a wall of an optical analysisarea rather than at a center of the optical analysis area can increasethe amount of light detected by, and hence, strength of signal generatedfrom, an optical detector positioned to receive light from the opticalanalysis area. For example, the strength of signal generated by anoptical detector positioned to receive light from the optical analysisarea may be from approximately 2 to approximately 5 times stronger whenthe optical emitter is offset to direct light adjacent a wall of anoptical analysis area rather than at a center of the optical analysisarea. Increased signal strength may be useful for a variety of reasons.As one example, in applications where fouling builds up on an opticaldetector during service, the ability to generate stronger signals canextend the length of time the optical sensor can remain in servicebetween cleaning and maintenance.

Without wishing to be bound by any particular theory, it is believedthat offsetting an optical emitter relative to a center of an opticalanalysis area may reduce the amount of light that is reflected in theoptical analysis area (e.g., due to turbidity of the fluid sample and/orreflection off internal or external surfaces of the optical analysisarea) as compared to if the optical emitter is positioned to directlight at the center of an optical analysis area. In turn, this canincrease the strength of the signal generated by one or more opticaldetectors surrounding the optical analysis area.

FIG. 6 is a cross-sectional drawing showing an alternative configurationof sensor 300 in which the optical emitter has been offset relative tothe center of the optical analysis area. Like components of sensor 300in FIGS. 3-6 are identified by like reference numbers. For example,sensor 300 in FIG. 6 is illustrated as including optical emitter 350,first optical detector 352, second optical detector 356, and thirdoptical detector 358. Optical emitter 350 is positioned behind firstoptical window 324; first optical detector 352 is positioned behindsecond optical window 326; second optical detector 356 is positionedbehind third optical window 328; a third optical detector 358 positionedbehind fourth optical window 330. Optical windows 324, 326, 328, 330each face optical analysis area 314 to direct light into and receivelight from a fluid sample present in the optical analysis area. Inaddition, sensor 300 in FIG. 6 includes optical filters 225 (FIG. 2)positioned between the optical emitter/detectors and optical windows324, 326, 328, 330. In other examples, sensor 300 may not include theoptical filters or may have a different number or arrangement of opticalfilters.

In contrast to the configuration of optical sensor 300 in FIG. 5, in theexample configuration of FIG. 6, first optical window 324 (e.g., theoptical emitter window) is offset relative to a center of opticalanalysis area 314. In particular, first optical window 324 is positionedcloser to fourth optical window 330 (e.g., the third optical detectorwindow) than third optical window 328 (e.g., the second optical detectorwindow). In operation, light emitted by optical emitter 350 andtraveling in a linear direction through a geometric center of firstoptical window 324 may not be directed at nor intersect a geometriccenter of optical analysis area 314. Rather, by offsetting opticalemitter window 324, the light may be directed closer to a wall ofoptical analysis area 314 than if the light were directed at a geometriccenter of the optical analysis area.

For example, in FIG. 6, optical analysis area 314 defines a geometriccenter 388. The geometric center 388 may be an arithmetic mean locationof all points around the perimeter bounding the optical analysis area.For instance, where optical analysis area 314 is a circular tube, thegeometric center 388 may be a point in the interior of the circle thatis equidistance from all points on the circumference of the circle. Byoffsetting first optical window 324 relative to geometric center 388,light emitted through the optical analysis window may not converge atthe geometric center of the optical analysis area. Rather, the light mayconverge at a location between the geometric center 388 of opticalanalysis area 314 and a wall bounding the optical analysis area.

In the example of FIG. 6, optical analysis area 314 is illustrated as afluid tube (e.g., glass tube, quartz tube, sapphire tube) that definesan internal diameter 390 and an external diameter 392, where theinternal diameter is separated from the external diameter by a wallthickness of the tube. Optical windows 324, 326, 328, and 330 arepositioned adjacent to and, in some examples, in contact with anexternal surface of the fluid tube. In addition, in FIG. 6, opticalwindows 324, 326, 328, and 330 are ball lenses that have a diameterlarger than the internal diameter 390 of the fluid tube. Otherconfigurations of optical windows 324, 326, 328, and 330 and opticalanalysis area 314 are possible for sensor 300.

Optical emitter 350 and/or first optical window 324 can be offsetrelative to a geometric center of optical analysis area 314 in a varietyof different ways. In the example of FIG. 6, optical emitter 350 andfirst optical window 324 are moved in the negative Y-direction relativeto second optical window 326 so that light traveling linearly from ageometric center of first optical window is directed closer to thirdoptical detector 358 than second optical detector 356. In otherexamples, optical emitter 350 and first optical window 324 may be movedin the positive Y-direction relative to second optical window 326 sothat light traveling linearly from a geometric center of first opticalwindow 324 is directed closer to second optical detector 356 than thirdoptical detector 358.

In some examples, optical emitter 350 and/or first optical window 324 ispositioned so that an axis 380 (FIG. 5) located in a common plane ofoptical windows 324, 326, 328, 330 and extending through a geometriccenter of first optical window 324 does not intersect an axis 382 thatis located in the common plane of optical windows 324, 326, 328, 330 andthat extends through a geometric center of second optical window 326.While the distance first optical window 324 is offset relative togeometric center 388 may vary, e.g., based on the size of the opticalwindow and the configuration of the sensor, in some examples, geometriccenter of the first optical window is offset (e.g., in the positive ornegative Y-direction indicated on FIG. 6) from geometric center 388 adistance ranging from approximately 0.5 millimeters to approximately 10millimeters, such as a distance ranging from approximately 1 millimeterto approximately 3 millimeters. Positioning first optical window 324 sothat light emitted by optical emitter 350 is directed adjacent a wall ofoptical analysis area 314 may increase the strength of the signalsgenerated by optical detectors 352, 356, 358.

The strength of signals detected by optical detectors 352, 356, 358 willvary, e.g., depending on the design of the specific detectors and theconfiguration of optical sensor 300. In one example in which opticalsensor 300 is arranged as illustrated in FIG. 6 (and where opticalanalysis area 314 is a quartz tube having a 3 mm internal diameter and a5 mm external diameter and first optical window 224 is offset in thenegative Y-direction by 1 mm), it is expected that third opticaldetector 358 will provide a fluorescence signal of 19.9—micro-Watts(μW). By contrast, if optical windows 324, 326, 328, and 330 weresymmetrical around optical analysis area 314 so that first opticalwindow 224 was not offset in the negative Y-direction, it is expectedthat third optical detector 358 would provide a fluorescence signal of10.5 μW under similar conditions (e.g., similar fluid flowing throughoptical analysis area 314).

FIG. 7 illustrates yet another example arrangement of optical sensor300. Optical sensor 300 in FIG. 7 is the same as the optical sensor inFIG. 6 except that fourth optical window 330 and third optical detector358 have been moved in the negative X-direction. In one example in whichoptical sensor 300 is arranged as illustrated in FIG. 7 (and whereoptical analysis area 314 is a quartz tube having a 3 mm internaldiameter and a 5 mm external diameter, first optical window 224 isoffset in the negative Y-direction by 1 mm, fourth optical window isoffset in the negative X-direction 1 mm, and third optical detector 358is offset in the negative X-direction 2.5 mm), it is expected that thirdoptical detector 358 will provide a fluorescence signal of 22.2 μW whentested under similar conditions as discussed above with respect to theexample in connection with FIG. 6. This is higher than when allcomponents are symmetrical around optical analysis area 314 and whenonly first optical 324 is offset.

The techniques described in this disclosure may be implemented, at leastin part, in hardware, software, firmware or any combination thereof. Forexample, various aspects of the described techniques may be implementedwithin one or more processors, including one or more microprocessors,digital signal processors (DSPs), application specific integratedcircuits (ASICs), field programmable gate arrays (FPGAs), or any otherequivalent integrated or discrete logic circuitry, as well as anycombinations of such components. The term “processor” may generallyrefer to any of the foregoing logic circuitry, alone or in combinationwith other logic circuitry, or any other equivalent circuitry. A controlunit comprising hardware may also perform one or more of the techniquesof this disclosure.

Such hardware, software, and firmware may be implemented within the samedevice or within separate devices to support the various operations andfunctions described in this disclosure. In addition, any of thedescribed units, modules or components may be implemented together orseparately as discrete but interoperable logic devices. Depiction ofdifferent features as modules or units is intended to highlightdifferent functional aspects and does not necessarily imply that suchmodules or units must be realized by separate hardware or softwarecomponents. Rather, functionality associated with one or more modules orunits may be performed by separate hardware or software components, orintegrated within common or separate hardware or software components.

The techniques described in this disclosure may also be embodied orencoded in a non-transitory computer-readable medium, such as acomputer-readable storage medium, containing instructions. Instructionsembedded or encoded in a computer-readable storage medium may cause aprogrammable processor, or other processor, to perform the method, e.g.,when the instructions are executed. Non-transitory computer readablestorage media may include volatile and/or non-volatile memory formsincluding, e.g., random access memory (RAM), read only memory (ROM),programmable read only memory (PROM), erasable programmable read onlymemory (EPROM), electronically erasable programmable read only memory(EEPROM), flash memory, a hard disk, a CD-ROM, a floppy disk, acassette, magnetic media, optical media, or other computer readablemedia.

Various examples have been described. These and other examples arewithin the scope of the following claims.

1. An optical sensor comprising: an optical emitter that is configuredto direct light into a fluid sample; a first optical detector that isconfigured to detect light emitted by the optical emitter andtransmitted through the fluid sample; a second optical detector that isconfigured to detect light emitted by the optical emitter and scatteredby the fluid sample; a third optical detector that is configured todetect fluorescent emissions emitted by the fluid sample in response tothe light emitted by the optical emitter; an optical emission filterpositioned between the optical emitter and the fluid sample; a firstoptical detection filter positioned between the first optical detectorand the fluid sample; a second optical detection filter positionedbetween the second optical detector and the fluid sample; and a thirdoptical detection filter positioned between the third optical detectorand the fluid sample, wherein the optical emission filter, the firstoptical detection filter, and the second optical detection filter areeach configured to filter out the same wavelengths of light so thatsubstantially any light detected by the first optical detector and thesecond optical detector is light emitted from the optical emitter andpassing through the fluid sample.
 2. The sensor of claim 1, wherein thethird optical filter is configured to filter out substantially all thewavelengths of light emitted by the optical emitter and passing throughthe optical emission filter.
 3. The sensor of claim 1, wherein theoptical emission filter, the first optical detection filter, and thesecond optical detection filter are each configured to filter outwavelengths of light greater than approximately 300 nanometers.
 4. Thesensor of claim 1, further comprising a housing that defines an opticalanalysis area through which the fluid sample can travel for opticalanalysis, the housing including an optical emitter assembly that carriesthe optical emitter, a first optical emitter assembly that carries thefirst optical emitter, a second optical emitter assembly that carriesthe second optical emitter, and a third optical emitter assembly thatcarries the third optical emitter.
 5. The sensor of claim 4, wherein thehousing further comprises an optical emitter window positioned betweenthe optical emitter and the optical analysis area, a first opticaldetector window positioned between the first optical detector and theoptical analysis area, a second optical detector window positionedbetween the second optical detector and the optical analysis area, and athird optical detector window positioned between the third opticaldetector and the optical analysis area.
 6. The sensor of claim 5,wherein the first optical detector window is positioned on an oppositeside of the optical analysis area from the optical emitter window, thesecond optical detector window is positioned at an approximately 90degree angle relative to the optical emitter window, and the thirdoptical detector window is positioned on an opposite side of the opticalanalysis area from the second optical detector window.
 7. The sensor ofclaim 5, wherein the optical analysis area comprises a tube that has aninner diameter and an outer diameter, and wherein the optical emitterwindow, the first optical detector window, the second optical detectorwindow, and the third optical detector window each comprise a ball lenspositioned to face the outer diameter of the tube.
 8. The sensor ofclaim 7, wherein the tube defines a geometric center through which thefluid sample travels, and the optical emitter window is offset relativeto the geometric center of the tube so that light emitted through ageometric center of the ball lens of the optical emitter window does notpass through the geometric center of the tube.
 9. The sensor of claim 7,wherein the second optical detector window is positioned at anapproximately 90 degree angle relative to the optical emitter window,the third optical detector window is positioned on an opposite side ofthe tube from the second optical detector window, and the opticalemitter window is offset so the geometric center of the optical emitterwindow is positioned closer to the third optical detector window thanthe second optical detector window.
 10. The sensor of claim 1, furthercomprising a temperature sensor, a pH sensor, and a conductivity sensor.11. The sensor of claim 10, wherein electronics for the temperaturesensor are positioned on a circuit board that contains one of the first,second, or third optical detectors, electronics for the pH sensor are ona circuit board that contains a different one of the first, second, orthird optical detectors, and electronics for the conductivity sensor areon a circuit board that contains yet a different one of the first,second, or third optical detectors.
 12. A method comprising: emittinglight into a fluid sample via an optical emitter; detecting lightemitted from the optical emitter and transmitted through the fluidsample via a first optical detector; detecting light emitted from theoptical emitter and scattered by the fluid sample via a second opticaldetector; and detecting fluorescent emissions emitted by the fluidsample in response to light emitted by the optical emitter via a thirdoptical detector, wherein detecting light via the first optical detectorand detecting light via the second optical detector further comprisesfiltering the light so that substantially any light detected by thefirst optical detector and the second optical detector is light emittedfrom the optical emitter and passing into the fluid sample.
 13. Themethod of claim 12, wherein detecting fluorescent emissions via thethird optical detector further comprises filtering out substantially allwavelengths of light emitted by the optical emitter and passing into thefluid sample.
 14. The method of claim 12, wherein detecting light viathe first optical detector comprises detecting light on an opposite sideof an optical analysis area from where the optical emitter ispositioned, detecting light via the second optical detector comprisesdetecting light at an approximately 90 degree angle relative to wherethe optical emitter is positioned, and detecting fluorescent emissionsvia the third optical detector comprises detecting fluorescent emissionson an opposite side of the optical analysis area from where the secondoptical detector is positioned.
 15. The method of claim 12, whereinemitting light via the optical emitter comprises emitting light througha ball lens so that light passing through a geometric center of the balllens is not directed at a geometric center of an optical analysis area.16. The method of claim 12, wherein emitting light via the opticalemitter comprises emitting light through an optical window so that lightpassing through a geometric center of the optical window is directedcloser to the third optical detector than the second optical detector.17. An optical sensor system comprising: a housing that defines anoptical analysis area through which a fluid sample travels for opticalanalysis, the housing including an optical emitter assembly that carriesan optical emitter configured to direct light into the fluid sample, afirst optical emitter assembly that carries a first optical detectorconfigured to detect light emitted by the optical emitter andtransmitted through the fluid sample, a second optical emitter assemblythat carries a second optical detector configured to detect lightemitted by the optical emitter and scattered by the fluid sample, and athird optical emitter assembly that carries a third optical detectorconfigured to detect fluorescent emissions emitted by the fluid samplein response to the light emitted by the optical emitter, wherein thehousing includes an optical emitter window positioned between theoptical emitter and the optical analysis area, a first optical detectorwindow positioned between the first optical detector and the opticalanalysis area, a second optical detector window positioned between thesecond optical detector and the optical analysis area, and a thirdoptical detector window positioned between the third optical detectorand the optical analysis area, and the first optical detector window ispositioned on an opposite side of the optical analysis area from theoptical emitter window, the second optical detector window is positionedat an approximately 90 degree angle relative to the optical emitterwindow, and the third optical detector window is positioned on anopposite side of the optical analysis area from the second detectorwindow.
 18. The system of claim 17, further comprising an opticalemission filter positioned between the optical emitter and the opticalanalysis area, a first optical detection filter positioned between thefirst optical detector and the optical analysis area, a second opticaldetection filter positioned between the second optical detector and theoptical analysis area, and a third optical detection filter positionedbetween the third optical detector and the optical analysis area,wherein the optical emission filter, the first optical detection filter,and the second optical detection filter are each configured to filterout the same wavelengths of light so that substantially any lightdetected by the first optical detector and the second optical detectoris light emitted from the optical emitter and passing through theoptical analysis area.
 19. The system of claim 18, wherein the thirdoptical filter is configured to filter out substantially all thewavelengths of light emitted by the optical emitter and passing throughthe optical analysis area.
 20. The system of claim 17, wherein theoptical analysis area comprises a tube having an inner diameter and anouter diameter, and the optical emitter window, the first opticaldetection window, the second optical detection window, and the thirdoptical detection window each comprise a ball lens positioned to facethe outer diameter of the tube.
 21. The system of claim 17, wherein theoptical analysis area defines a geometric center through which the fluidsample travels, and the optical emitter window is offset relative to thegeometric center of the optical analysis area so that light emittedthrough a geometric center of the optical emitter window is not directedto pass through the geometric center of the optical analysis area. 22.The system of claim 17, wherein the optical emitter window is offset soa geometric center of the optical emitter window is positioned closer tothe third optical detector window than the second optical detectorwindow.